1. Field of the Invention
The present invention relates to managing electromagnetic interference in electronic devices.
2. Background of the Related Art
Electromagnetic interference (EMI) refers to interference with electronic circuits caused by noise in the electromagnetic frequency spectrum. Some sources of EMI are naturally occurring, such as radiation from the sun, but EMI affecting an electrical circuit is typically caused by other nearby electronic circuitry. Commercial electronic equipment, such as computers and transmitters, are common sources of electromagnetic noise. Other potential sources of EMI include radio transmitters, power lines, electronic circuits, electric motors, and other devices that utilize or detect electromagnetic energy. EMI can propagate from the source to the affected circuit by radiation or induction. For example, data center equipment, such as a network switch, may generate EMI that disturbs circuits in other data center equipment through radiation. EMI generated by a particular piece of equipment may even affect circuits within that same piece of equipment, through induction. Examples of undesirable responses in an electrical circuit caused by EMI include interruption, obstruction, or other degradation of the intended performance of the electrical circuit.
Electromagnetic compatibility (EMC) is a branch of electrical science and engineering concerned with managing EMI to ensure that equipment functions properly within expected levels of electromagnetic radiation in the intended environment of use. For example, in a data center, EMC may focus on ensuring that a densely-packed rack of servers are not adversely affected by any electromagnetic radiation generated by the servers. EMC may also focus on circuits within a specific device component, such as to prevent a high-speed signal on an integrated circuit from affecting or being affected by electrical activity of micro-components within the same integrated circuit. Thus, the field of EMC helps to ensure that a device or system functions without error in its intended electromagnetic environment.
The problems associated with EMI in electronic equipment have led to the promulgation of regulations by standards bodies, such as FCC (Federal Communications Commission) regulations in the United States, EC (European Commission) regulations in Europe, and VCCI (Voluntary Control Council for Interference by Information Technology Equipment) regulations in Japan. Such regulations include electromagnetic emissions limits on electronic equipment. To comply with these regulations, equipment manufacturers have taken steps to reduce electromagnetic emissions, such as by using shielded modular connector jacks. Shielded modular connector jacks have an electrically conductive skin made of metal that protects a connector from emissions by neighboring connectors. Despite such built-in shielding devices, electronic equipment will commonly have some unused and exposed connectors while in service. These exposed connectors contribute to the EMI risks in electronic equipment while in use.